The present invention relates to the diagnostic imaging art. It finds particular application in conjunction with nuclear single photon emission computed tomography (SPECT) medical imaging and will be described with particular reference thereto. However, the invention will also find application in conjunction with other types of non-invasive diagnostic imaging.
Heretofore, diagnostic images have been generated from single and multiple-head nuclear cameras. Typically, a patient positioned in an examination region is injected with a radio pharmaceutical. Heads of the nuclear camera are positioned closely adjacent to the patient to monitor the radio pharmaceutical. Typically, the heads are stepped in increments of a few degrees around the patient until 360° of data have been acquired. That is, projection data along directions spanning 360° are collected. With multiple-head systems, projections along each direction need only be collected with one of the heads and be assembled into a complete data set.
Each detector head carries a collimator which defines a path along which it can receive radiation. However, due to the finite length and dimensions of the collimator, each incremental area of the detector head actually views an expanding cone. Thus, with increasing depth into the patient away from the detector head, the region from which a sensed radiation event originated expands. This creates depth-dependent blurring and uncertainty in the resultant image data. This error is a non-stationary convolution which is difficult to deconvolve. However, when the patient is viewed over a full 360°, the angular data sets are periodic in 2π radians. By transforming the full data sets into the frequency domain with a Fourier transform fit to the sampling intervals, the non-stationary deconvolution is reduced to a stationary deconvolution problem, particularly for high frequencies.
Although these prior art resolution recovery techniques work well on full data sets, cardiac imaging is typically done using an incomplete data set. More specifically, in a three-head camera system where only two heads collect the emission data while the third head is used to collect transmission data, the gantry is rotated by about 102° to generate the equivalent of only about 204° of emission data. The prior art resolution recovery techniques do not work on partial data sets whose data is not periodic in 2π radians.
The present invention contemplates a new and improved method and apparatus which overcomes the above-referenced problems and others.